CN114034971A - Method, system, device and medium for processing line fault in low-frequency power transmission system - Google Patents
Method, system, device and medium for processing line fault in low-frequency power transmission system Download PDFInfo
- Publication number
- CN114034971A CN114034971A CN202111257577.7A CN202111257577A CN114034971A CN 114034971 A CN114034971 A CN 114034971A CN 202111257577 A CN202111257577 A CN 202111257577A CN 114034971 A CN114034971 A CN 114034971A
- Authority
- CN
- China
- Prior art keywords
- line
- frequency
- phase
- low
- power transmission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
Abstract
The invention discloses a method, a system, a device and a medium for processing line faults in a low-frequency power transmission system, wherein the method comprises the following steps: determining that a first phase line in the low-frequency lines is detected to be in fault, and cutting off the first phase line; adjusting a second-phase line and a third-phase line in the low-frequency line into an orthogonal two-phase power transmission mode so as to avoid active power frequency doubling fluctuation components; the low-frequency power transmission system comprises a power frequency main network and a low-frequency circuit, the low-frequency circuit is connected with the power frequency main network through an MMMC converter station, and the MMMC converter station comprises a modular multi-level matrix converter and a converter transformer. When a line in a low-frequency line has a fault, the original three-phase power transmission mode is converted into a two-phase power transmission mode, so that the loss of transmission power is avoided; in addition, the phase of a sound two-phase line is adjusted to enter an orthogonal two-phase power transmission mode, so that a double-frequency fluctuation component is avoided, and the system stability is favorably maintained. The invention can be widely applied to the technical field of AC/AC conversion.
Description
Technical Field
The invention relates to the technical field of AC/AC conversion, in particular to a method, a system, a device and a medium for processing a line fault in a low-frequency power transmission system.
Background
Voltage and frequency are the two most important parameters of alternating current electrical energy. Since the transformer is invented, people can select different voltage levels from power generation, power transmission to power utilization according to needs, and the purposes of improving efficiency and facilitating use are achieved. However, the frequency is not fully utilized, and can only be 50Hz or 60 Hz. If different frequencies can be adopted in links of power generation, power transmission, power utilization and the like, great benefits can be brought into play; for example, the transmission capacity of the line can be greatly improved if the lower frequency is adopted for long-distance power transmission; if the electric energy is used at a higher frequency, the volume and weight of the electric equipment can be remarkably reduced, and energy and raw materials can be saved. The transmission power limit of the ac transmission system may be estimated using the following equation:
wherein: u is the rated voltage of the power transmission system, and X is the reactance of the power transmission system.
From the above equation we can see that the transmission power of the transmission line is proportional to the square of the rated voltage of the transmission system and inversely proportional to the reactance X of the system. Therefore, in order to increase the transmission power, the voltage may be increased, the reactance may be decreased, and it is obvious that decreasing the frequency of the transmission system increases the transmission power limit of the system in inverse proportion.
Due to the development of power electronic technology, a Modular Multi-Level matrix Converter (MMMC) has been widely used in the field of flexible power transmission, and the MMMC is adopted to switch power transmission to a lower frequency and achieve a better effect. For the traditional MMMC control strategy, if a low-frequency line of the traditional MMMC control strategy has a single-phase fault, a converter is directly locked, and the strategy can cause that the current transmission power of a system is completely lost, so that overlarge impact is caused on the system; if the two healthy phases are kept to enter the asymmetric operation mode, the phase difference of the two healthy phases is 120 degrees under the existing control strategy, and the double-frequency pulsation of active power caused by negative sequence voltage and current components is not beneficial to the stability of the system.
Disclosure of Invention
To solve at least one of the technical problems in the prior art to a certain extent, an object of the present invention is to provide a method, a system, a device and a medium for processing a line fault in a low frequency power transmission system.
The technical scheme adopted by the invention is as follows:
a method for processing line faults in a low-frequency power transmission system comprises the following steps:
determining that a first phase line in the low-frequency lines is detected to be in fault, and cutting off the first phase line;
adjusting a second-phase line and a third-phase line in the low-frequency line into an orthogonal two-phase power transmission mode so as to avoid active power frequency doubling fluctuation components;
the low-frequency power transmission system comprises a power frequency main network and a low-frequency circuit, the low-frequency circuit is connected with the power frequency main network through an MMMC converter station, and the MMMC converter station comprises a modular multi-level matrix converter and a converter transformer.
Further, the cutting off the first phase line includes:
disconnecting the first phase line by a circuit breaker;
the circuit breakers are mounted at two ends of the first phase line, the second phase line and the third phase line.
Further, the power transmission method of adjusting the second phase line and the third phase line in the low frequency line to be orthogonal includes:
the phase difference between the second phase line and the third phase line is adjusted from 120 degrees to 90 degrees through a control system of the modular multilevel matrix converter, and a current loop is formed by grounding through a neutral point in a low-frequency line so as to form an orthogonal two-phase power transmission mode.
Further, when the low-frequency line is in a three-phase power transmission mode, an expression of total power transmitted by the line is as follows:
wherein E isLIs a single phase voltage amplitude; i isLIs the line current amplitude;
is the low frequency side power factor angle.
Further, when the low-frequency line is in an orthogonal two-phase power transmission mode, an expression of total power transmitted by the line is as follows:
wherein E isLIs a single phase voltage amplitude; i isLIs the line current amplitude;
is the low frequency side power factor angle.
The other technical scheme adopted by the invention is as follows:
a system for handling line faults in a low frequency power transmission system, comprising:
the fault detection module is used for determining that a first phase line in the low-frequency line is detected to have a fault and cutting off the first phase line;
the line adjusting module is used for adjusting a second-phase line and a third-phase line in the low-frequency line into an orthogonal two-phase power transmission mode so as to avoid active power frequency doubling fluctuation components;
the low-frequency power transmission system comprises a power frequency main network and a low-frequency circuit, the low-frequency circuit is connected with the power frequency main network through an MMMC converter station, and the MMMC converter station comprises a modular multi-level matrix converter and a converter transformer.
Further, the cutting off the first phase line includes:
disconnecting the first phase line by a circuit breaker;
the circuit breakers are mounted at two ends of the first phase line, the second phase line and the third phase line.
Further, the power transmission method of adjusting the second phase line and the third phase line in the low frequency line to be orthogonal includes:
the phase difference between the second phase line and the third phase line is adjusted from 120 degrees to 90 degrees through a control system of the modular multilevel matrix converter, and a current loop is formed by grounding through a neutral point in a low-frequency line so as to form an orthogonal two-phase power transmission mode.
The other technical scheme adopted by the invention is as follows:
a device for handling line faults in a low frequency power transmission system, comprising:
at least one processor;
at least one memory for storing at least one program;
when executed by the at least one processor, cause the at least one processor to implement the method described above.
The other technical scheme adopted by the invention is as follows:
a computer readable storage medium in which a processor executable program is stored, which when executed by a processor is for performing the method as described above.
The invention has the beneficial effects that: when a line in a low-frequency line has a fault, the converter is not directly locked, but the original three-phase power transmission mode is converted into a two-phase power transmission mode, so that the loss of transmission power is avoided; in addition, the phase of a sound two-phase line is adjusted to enter an orthogonal two-phase power transmission mode, so that a double-frequency fluctuation component is avoided, and the system stability is favorably maintained.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description is made on the drawings of the embodiments of the present invention or the related technical solutions in the prior art, and it should be understood that the drawings in the following description are only for convenience and clarity of describing some embodiments in the technical solutions of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic circuit topology of an MMMC in an embodiment of the invention;
FIG. 2 is a schematic diagram of an application scenario of a three-phase end-to-end low-frequency power transmission system based on MMMC in the embodiment of the present invention;
fig. 3 is a schematic diagram of a converted orthogonal two phase end-to-end low frequency power transmission system in an embodiment of the invention;
fig. 4 shows typical waveforms of the voltage and current of the low-frequency power transmission system and MMMC bridge arm in the orthogonal two-phase operating mode according to the embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention. The step numbers in the following embodiments are provided only for convenience of illustration, the order between the steps is not limited at all, and the execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.
In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.
The circuit structure and the operation principle of the Modular Multilevel Matrix Converter (MMMC) will be explained below with reference to fig. 1. The MMMC comprises 9 bridge arms which connect the three-phase ports of the alternating current power grids on two sides in pairs. Each bridge arm is formed by connecting an inductor L and n full-bridge modules (FBSM) in series. In the embodiment, u, v and w represent three phases of a power frequency system, and a, b and c represent three-phase voltages of a frequency division system. For the purpose of simplifying the description, the subsequent part will refer to any one of the three phases a, b and c on the low frequency side with x, and refer to any one of the three phases u, v and w on the power frequency side with y. Each bridge arm is named by the name of the port to which both ends thereof are connected, and for example, the bridge arm connecting the frequency-dividing side a-phase and the power-frequency side u-phase is referred to as "bridge arm au". Each module consists of a module capacitor and a single-phase full-bridge inverter, and can output + v by changing the switching signals of four converter valves in the full-bridge inverterC，-vCOr 0 three levels (v)CModule capacitance voltage), if the capacitance voltage difference between the modules is ignored, nSMA module can generate a slave-nSMvCTo nSMvCIn between (2n +1) levels. Wherein, the bridge arm: the MMMC comprises 9 bridge arms in total, wherein the bridge arms are au, av, aw, bu, bv, bw, cu, cv and cw respectively.
According to kirchhoff's voltage law, a voltage output equation on the low-frequency side of the MMMC can be established:
in the formula, exRepresenting the voltage (x belongs to { u, v, w }) of the x-phase port at the power frequency side; e.g. of the typeyRepresenting the voltage of a y-phase port at the low-frequency side (y belongs to { a, b, c }); v. ofxyAnd ixyThe output voltage of the cascaded FBSM of the bridge arm xy and the current flowing through the bridge arm are respectively shown.
From above, vxyThe control can be realized by adjusting the trigger pulse of each FBSM to which the bridge arm belongs, and the control can be equivalent to a controlled voltage source. Further, a low frequency side three-phase voltage ea，ebAnd ecAlso in a fully controlled manner, i.e. for a given mains voltage eu，evAnd ewAnd a low-frequency side three-phase voltage command value ea ref，eb refAnd ec refAnd adjusting the output voltage of the cascaded FBSM in each bridge arm according to the rule of the formula (2), namely enabling the low-frequency side to output the required three-phase voltage:
the MMMC shown in the figure 1 is applied to a power frequency system, and a three-phase end-to-end low-frequency power transmission system based on the MMMC can be built, as shown in the figure 2. Based on the low-frequency power transmission system, in the method, after a fault of a phase line on a low-frequency side is detected, a converter is not directly locked, an original three-phase power transmission mode is converted into an orthogonal two-phase power transmission mode, namely, a phase line with a fault occurrence is switched and opened, a control system is converted into orthogonal two-phase power transmission, namely, the phase difference of sound two phases (namely, two-phase lines which are not cut off) is 90 degrees, a loop is formed by a neutral point grounding system, and active power passing through the low-frequency line in the mode does not contain a double-frequency component, so that the power stability of the system is favorably maintained. This is explained in detail below with reference to fig. 3.
Assuming normal operation, the low-frequency side three-phase voltage is:
in the formula, ELIs a single phase voltage amplitude; omegaLIs the low frequency system angular frequency.
The low-frequency side three-phase current is:
in the formula ILIs the line current amplitude;
is the low frequency side power factor angle.
The total power delivered by the line can be expressed as:
as can be seen from equation (5), during normal operation, the power transmitted by the three-phase line is a constant amount.
The operation of the low frequency system following a single phase line fault is discussed below. Without loss of generality, assuming that a fault occurs in a c-phase, after the fault is detected, the c-phase line is tripped through the action of circuit breakers at two ends of the line, and at the moment, the c-phase transmission power is 0. If the two phases a and b still operate 120 ° out of phase, the total power transmitted by the line can be expressed as:
as can be seen from equation (6), in this mode, the line transmission power includes a dc component and a frequency doubling ripple component, and the magnitude of the dc component is 2/3 in the case of three-phase health. The existence of the double frequency fluctuation component brings challenges to the safe and stable operation of the power transmission system.
If the electric quantities of the a phase and the b phase are 90 degrees different under the orthogonal two-phase operation mode of the a phase and the b phase, namely:
the total power delivered by the line at this time can be expressed as:
it can be seen that in the proposed operation mode, the line transmission power only includes a dc component, and its magnitude is the same as that of equation (6). Compared with the traditional open-phase operation mode, the provided operation mode eliminates the double-frequency fluctuation component of active power on the premise of maintaining the transmission power unchanged, and is favorable for the safe and stable operation of the system.
Referring to fig. 2, the MMMC-based three-phase end-to-end low-frequency power transmission system comprises a power frequency system, a converter station and a low-frequency power transmission line. Wherein, power frequency system does: in the embodiment, u, v and w denote power frequency three phases. The converter station consists of an MMMC frequency conversion device and Y-delta converter transformers on two sides; the MMMC is responsible for realizing frequency conversion between a power frequency system and a low frequency system, the output voltage of the low frequency side of the MMMC is controlled, and the MMMC can adjust the phase difference of two sound phases to be 90 degrees after a low frequency side line has a single-phase fault, so as to realize orthogonal two-phase operation; the Y-delta converter transformer realizes the voltage conversion between the MMMC port voltage and the power frequency and low frequency system, and simultaneously plays an isolation role. Based on the three-phase end-to-end low-frequency power transmission system, the method for processing the line fault in the low-frequency power transmission system provided by the embodiment includes the following steps:
and S1, determining that the first phase line in the low-frequency line is detected to be in fault, and cutting off the first phase line.
The fault detection can be performed by the existing line protection system, and the existing power system relay protection framework has a mature technical scheme, so that the details are not repeated herein. It should be noted that the first phase line does not specifically designate a certain line in the three-phase lines, but refers to a failed line, for example, if line a fails, line a is the first phase line, and the remaining lines b and c are healthy two lines; if the line b has a fault, the line b is the first phase line, and the remaining lines a and c are two healthy lines.
In some optional embodiments, the fault phase low-frequency line is tripped through circuit breakers at two ends of the line, so that the original three-phase power transmission mode is converted into a two-phase power transmission mode.
And S2, adjusting the second-phase line and the third-phase line in the low-frequency line to be in an orthogonal two-phase power transmission mode so as to avoid the active power double-frequency fluctuation component.
In this embodiment, when a single-phase fault occurs in the low-frequency transmission line, the healthy two phases no longer maintain a phase difference of 120 °, but the phase difference of the healthy two phases on the primary side of the low-frequency system is adjusted to 90 ° by adjusting the output voltage on the low-frequency side of the MMMC, and a current loop is formed through the neutral point grounding system, so as to enter an orthogonal two-phase power transmission mode.
The above method is explained in detail with reference to specific examples below.
If a single-phase fault occurs in the low-frequency line, for example, the phase a of the low-frequency line is permanently grounded, the corresponding method is as follows:
the first step is as follows: because the sub-converter a is connected with the phase a at the low-frequency side, when the line protection system detects a phase a fault, the protection at the two sides of the line can be tripped to isolate the line fault, and the primary side of the low-frequency system enters a two-phase operation mode. Wherein, the sub-converter: the MMMC is composed of 3 bridge arms connected with the same phase of an alternating current system, and has 3 sub-converters, namely a sub-converter a (au, av and aw), a sub-converter b (bu, bv and bw) and a sub-converter c (cu, cv and cw), when viewed from the low frequency side.
The second step is that: and after the converter station detects the fault or receives fault information, the maximum power of the MMMC is limited to 2/3 of a designed value.
And thirdly, smoothly switching the control system to a corresponding orthogonal two-phase power transmission mode according to the fault phase, adjusting the output voltages of the sub-converters a, b and c to match the secondary side three-phase voltage when the primary side orthogonal two-phase power transmission mode operates, and further finely adjusting the output voltages of the sub-converters a, b and c according to the requirements of feedback control links such as power/voltage/current and the like, as shown in fig. 4. Fig. 4(a) is a simulation schematic diagram of the low-frequency converter transformer line-side voltage, fig. 4(b) is a simulation schematic diagram of the MMMC low-frequency side outlet voltage, fig. 4(c) is a simulation schematic diagram of the low-frequency converter transformer line-side current, and fig. 4(d) is a simulation schematic diagram of the MMMC low-frequency side outlet current.
In summary, compared with the prior art, the method of the embodiment has the following beneficial effects: in the application scenario of end-to-end low-frequency power transmission based on MMMC, the control strategy is simple and easy to use, the method can be switched into an orthogonal two-phase power transmission mode after single-phase fault of an MMMC low-frequency line, active power transmitted after the fault does not contain double frequency fluctuation, system power and energy stability are facilitated, engineering practical value is achieved, and economic benefit is remarkable.
The present embodiment further provides a system for processing a line fault in a low-frequency power transmission system, including:
the fault detection module is used for determining that a first phase line in the low-frequency line is detected to have a fault and cutting off the first phase line;
the line adjusting module is used for adjusting a second-phase line and a third-phase line in the low-frequency line into an orthogonal two-phase power transmission mode so as to avoid active power frequency doubling fluctuation components;
the low-frequency power transmission system comprises a power frequency main network and a low-frequency circuit, the low-frequency circuit is connected with the power frequency main network through an MMMC converter station, and the MMMC converter station comprises a modular multi-level matrix converter and a converter transformer.
As a further optional implementation, the cutting off the first phase line includes:
disconnecting the first phase line by a circuit breaker;
the circuit breakers are mounted at two ends of the first phase line, the second phase line and the third phase line.
As a further optional implementation, the adjusting the second phase line and the third phase line in the low frequency line to be orthogonal power transmission mode includes:
the phase difference between the second phase line and the third phase line is adjusted from 120 degrees to 90 degrees through a control system of the modular multilevel matrix converter, and a current loop is formed by grounding through a neutral point in a low-frequency line so as to form an orthogonal two-phase power transmission mode.
The system for processing the line fault in the low-frequency power transmission system according to the embodiment of the invention can execute the method for processing the line fault in the low-frequency power transmission system provided by the embodiment of the method of the invention, can execute any combination of the implementation steps of the embodiment of the method, and has corresponding functions and beneficial effects of the method.
The present embodiment further provides a device for processing a line fault in a low-frequency power transmission system, including:
at least one processor;
at least one memory for storing at least one program;
when executed by the at least one processor, cause the at least one processor to implement the method described above.
The device for processing the line fault in the low-frequency power transmission system according to the embodiment of the invention can execute the method for processing the line fault in the low-frequency power transmission system provided by the embodiment of the invention, can execute any combination of the implementation steps of the embodiment of the method, and has corresponding functions and beneficial effects of the method.
The embodiment also provides a storage medium, which stores an instruction or a program capable of executing the method for processing the line fault in the low-frequency power transmission system provided by the embodiment of the method of the invention, and when the instruction or the program is executed, the method can be executed by any combination of the embodiment of the method, and the method has corresponding functions and beneficial effects.
In alternative embodiments, the functions/acts noted in the block diagrams may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Furthermore, the embodiments presented and described in the flow charts of the present invention are provided by way of example in order to provide a more thorough understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is changed and in which sub-operations described as part of larger operations are performed independently.
Furthermore, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise stated to the contrary, one or more of the described functions and/or features may be integrated in a single physical device and/or software module, or one or more functions and/or features may be implemented in a separate physical device or software module. It will also be appreciated that a detailed discussion of the actual implementation of each module is not necessary for an understanding of the present invention. Rather, the actual implementation of the various functional modules in the apparatus disclosed herein will be understood within the ordinary skill of an engineer, given the nature, function, and internal relationship of the modules. Accordingly, those skilled in the art can, using ordinary skill, practice the invention as set forth in the claims without undue experimentation. It is also to be understood that the specific concepts disclosed are merely illustrative of and not intended to limit the scope of the invention, which is defined by the appended claims and their full scope of equivalents.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.
It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
In the foregoing description of the specification, reference to the description of "one embodiment/example," "another embodiment/example," or "certain embodiments/examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method for processing line faults in a low-frequency power transmission system is characterized by comprising the following steps:
determining that a first phase line in the low-frequency lines is detected to be in fault, and cutting off the first phase line;
adjusting a second-phase line and a third-phase line in the low-frequency line into an orthogonal two-phase power transmission mode so as to avoid active power frequency doubling fluctuation components;
the low-frequency power transmission system comprises a power frequency main network and a low-frequency circuit, the low-frequency circuit is connected with the power frequency main network through an MMMC converter station, and the MMMC converter station comprises a modular multi-level matrix converter and a converter transformer.
2. The method for handling the line fault in the low-frequency power transmission system according to claim 1, wherein the disconnecting the first-phase line comprises:
disconnecting the first phase line by a circuit breaker;
the circuit breakers are mounted at two ends of the first phase line, the second phase line and the third phase line.
3. The method for processing the line fault in the low-frequency power transmission system according to claim 1, wherein the adjusting the second phase line and the third phase line in the low-frequency line to be orthogonal power transmission modes comprises:
the phase difference between the second phase line and the third phase line is adjusted from 120 degrees to 90 degrees through a control system of the modular multilevel matrix converter, and a current loop is formed by grounding through a neutral point in a low-frequency line so as to form an orthogonal two-phase power transmission mode.
4. The method for processing the line fault in the low-frequency power transmission system according to claim 1, wherein when the low-frequency line is in a three-phase power transmission mode, an expression of total power transmitted by the line is as follows:
wherein E isLIs a single phase voltage amplitude; i isLIs the line current amplitude;
is the low frequency side power factor angle.
5. The method according to claim 1, wherein when the low-frequency line is in an orthogonal two-phase power transmission mode, the expression of the total power transmitted by the line is as follows:
wherein E isLIs a single phase voltage amplitude; i isLIs the line current amplitude;
is the low frequency side power factor angle.
6. A system for handling line faults in a low frequency power transmission system, comprising:
the fault detection module is used for determining that a first phase line in the low-frequency line is detected to have a fault and cutting off the first phase line;
the line adjusting module is used for adjusting a second-phase line and a third-phase line in the low-frequency line into an orthogonal two-phase power transmission mode so as to avoid active power frequency doubling fluctuation components;
the low-frequency power transmission system comprises a power frequency main network and a low-frequency circuit, the low-frequency circuit is connected with the power frequency main network through an MMMC converter station, and the MMMC converter station comprises a modular multi-level matrix converter and a converter transformer.
7. The system for handling a line fault in a low frequency power transmission system of claim 6, wherein said disconnecting the first phase line comprises:
disconnecting the first phase line by a circuit breaker;
the circuit breakers are mounted at two ends of the first phase line, the second phase line and the third phase line.
8. The system for handling line faults in a low frequency power transmission system according to claim 6, wherein the adjusting of the second phase line and the third phase line in the low frequency line to an orthogonal power transmission mode comprises:
the phase difference between the second phase line and the third phase line is adjusted from 120 degrees to 90 degrees through a control system of the modular multilevel matrix converter, and a current loop is formed by grounding through a neutral point in a low-frequency line so as to form an orthogonal two-phase power transmission mode.
9. An apparatus for handling line faults in a low frequency power transmission system, comprising:
at least one processor;
at least one memory for storing at least one program;
when executed by the at least one processor, cause the at least one processor to implement the method of any one of claims 1-5.
10. A computer-readable storage medium, in which a program executable by a processor is stored, wherein the program executable by the processor is adapted to perform the method according to any one of claims 1 to 5 when executed by the processor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111257577.7A CN114034971B (en) | 2021-10-27 | 2021-10-27 | Method, system, device and medium for processing line fault in low-frequency power transmission system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111257577.7A CN114034971B (en) | 2021-10-27 | 2021-10-27 | Method, system, device and medium for processing line fault in low-frequency power transmission system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114034971A true CN114034971A (en) | 2022-02-11 |
| CN114034971B CN114034971B (en) | 2022-07-26 |
Family
ID=80135559
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111257577.7A Active CN114034971B (en) | 2021-10-27 | 2021-10-27 | Method, system, device and medium for processing line fault in low-frequency power transmission system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114034971B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116148589A (en) * | 2022-11-15 | 2023-05-23 | 合肥工业大学 | Simplified analysis method and system for fault current of low-frequency power transmission system |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPWO2014141353A1 (en) * | 2013-03-11 | 2017-02-16 | 株式会社日立製作所 | DC / DC converter |
| CN108718094A (en) * | 2018-05-24 | 2018-10-30 | 新疆大学 | A method of it improving large-sized photovoltaic system low-voltage and passes through performance |
| CN112269097A (en) * | 2020-09-23 | 2021-01-26 | 中国人民解放军海军工程大学 | Integrated power edge computing system and control method |
| CN113504430A (en) * | 2021-07-07 | 2021-10-15 | 广东电网有限责任公司 | Extra-high voltage direct current fault detection system |
-
2021
- 2021-10-27 CN CN202111257577.7A patent/CN114034971B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPWO2014141353A1 (en) * | 2013-03-11 | 2017-02-16 | 株式会社日立製作所 | DC / DC converter |
| CN108718094A (en) * | 2018-05-24 | 2018-10-30 | 新疆大学 | A method of it improving large-sized photovoltaic system low-voltage and passes through performance |
| CN112269097A (en) * | 2020-09-23 | 2021-01-26 | 中国人民解放军海军工程大学 | Integrated power edge computing system and control method |
| CN113504430A (en) * | 2021-07-07 | 2021-10-15 | 广东电网有限责任公司 | Extra-high voltage direct current fault detection system |
Non-Patent Citations (3)
| Title |
|---|
| PAVEL I. PUZYREV 等: "Orthogonal Phase-Coded Signals with Additional Differential Phase Shift Keying", 《2018 DYNAMICS OF SYSTEMS, MECHANISMS AND MACHINES》 * |
| 夏春 等: "面向城市电网扩容改造的双端型柔性分频输电系统M3C换流站建模与控制研究", 《浙江电力》 * |
| 石照民 等: "超低频电压量值溯源关键技术研究", 《计量科学与技术》 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116148589A (en) * | 2022-11-15 | 2023-05-23 | 合肥工业大学 | Simplified analysis method and system for fault current of low-frequency power transmission system |
| CN116148589B (en) * | 2022-11-15 | 2023-09-19 | 合肥工业大学 | Simplified analysis method and system for fault current of low-frequency power transmission system |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114034971B (en) | 2022-07-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP4131762A1 (en) | Interconnected co-phase traction power supply system based on four-port modular multilevel converter | |
| JP6181132B2 (en) | Power converter | |
| CN107947146B (en) | Direct-current power grid based on modular multilevel converter and multilayer fault-tolerant control method | |
| US7532490B2 (en) | Converter topology and methods for interfacing an electrical machine to electrical power grid | |
| CN109167364B (en) | Three-port flexible multi-state switching device based on bridge arm multiplexing and hybrid cascading | |
| CN113364311B (en) | Multi-medium-voltage alternating-current port solid-state transformer and control method thereof | |
| CN111446866B (en) | Through same-phase traction power supply system based on balancing transformer and four-port MMC | |
| CN102593841A (en) | Current separation compensation-based cascaded H-bridge distribution static synchronous compensator (DSTATCOM) device and separation compensation method | |
| Vozikis et al. | Steady-state performance of state-of-the-art modular multilevel and alternate arm converters with DC fault-blocking capability | |
| CN112383229A (en) | Multi-port power electronic transformer topological structure and alternating current-direct current micro-grid system thereof | |
| Sun et al. | Hybrid LCC-AAC HVDC transmission system | |
| CN114034971B (en) | Method, system, device and medium for processing line fault in low-frequency power transmission system | |
| EP3304710A1 (en) | Modular multilevel converter with cascaded h-bridges and phase-shifted transformer groups | |
| Venkat et al. | Operation of a three phase solid state-Transformer under unbalanced load conditions | |
| CN213585598U (en) | Multi-port power electronic transformer topological structure and alternating current-direct current micro-grid system thereof | |
| CN110048596A (en) | A kind of high-voltage frequency converter braking circuit topological structure | |
| CN115441750A (en) | Mixed type AC-AC converter | |
| CN114678884A (en) | Operation test method for low-frequency power transmission converter submodule | |
| CN113595128A (en) | Flexible ring network controller topology without connection transformer | |
| Kavya et al. | Comparison of controllers of hybrid HVDC link in multi-infeed application | |
| Yakupoglu et al. | Technical and economic comparison of HVDC converter technologies | |
| Adam et al. | Controlled transition bridge converter: Operating principle, control and application in HVDC transmission systems | |
| CN112072704B (en) | Medium-voltage high-capacity wind power generation converter topology | |
| Poikilidis et al. | Design of the inner AC circuit of a DC hub for the interconnection of multiple HVDC lines | |
| CN115473445A (en) | Mixed type AC-AC converter |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |